Chadwick Boseman was sitting in a New York City bar watching the final outs of a 2011 National League playoff game when it hit him: he was going to play baseball great Jackie Robinson.

There was no clear logic behind this epiphany. Sure, the actor had just auditioned for the lead role in 42, the first big-budget biopic about the modern major leagues’ first African-American player—the man who crossed the color line in 1947. But Boseman’s feature-film credits to that point consisted of a sole supporting role in the 2008 movie The Express. And though he had recurring roles on TV shows like NBC’s Persons Unknown and ABC Family’s Lincoln Heights, those series were hardly smash hits. What’s more, the actor, now 36, was having a rough year. Director after director had passed on him for parts he’d been sure he would nab.

So he wasn’t exactly a safe bet to star in a major studio film about one of the most important figures in the history of American sports. But as the St. Louis Cardinals celebrated their playoff win on the field, he suddenly felt their euphoria. “I’m about to play Jackie Robinson,” he told a friend at the bar. The pal gave him an incredulous look, and Boseman filled him in on the audition and his sudden certitude. A few other friends joined the conversation, and they all decided to toast Boseman for his role: one that he didn’t have yet and probably would never get.

Except that he did. On April 12, Boseman will make his rookie debut as leading man in 42, which also stars Harrison Ford as Branch Rickey, the gruff Brooklyn Dodgers president and general manager who brought Robinson to the majors.

Robinson’s story is familiar to many, but the movie unleashes the raw emotion behind the myth. The ballplayer endured unspeakable racial abuse after joining the Dodgers; a lesser man would have cracked. Boseman captures Robinson’s pain so well that his performance left some preview audience members in tears.

Boseman grew up in Anderson, S.C., a city of 26,000 in the foothills of the Blue Ridge Mountains where his mom is a nurse and his father owns an upholstery business. “No one is supposed to come from there and do this right here, what I’m doing,” he says.

Boseman wasn’t one of those movie-buff kids. Still, he says, shortly before graduating from high school, “I just decided that I would direct films, direct plays.” In what he calls a last-minute decision, he enrolled in the theater program at Howard University. He wrote a few plays after college, and he continues to write and direct smaller film and stage projects. But by 2008, he had gotten serious enough about pursuing film acting to head to Los Angeles. “I just knew at that point that I was ready to be here in this world,” he says.

It wasn’t easy going. “There were a whole lot of things I was on hold for that I thought I was going to get,” he says. “There were movies every year where I was like, Damn, I was supposed to be in that.” Boseman read for a supporting role in Quentin Tarantino’s Django Unchained, nominated for a Best Picture Oscar this year. He didn’t get it, but he made an impression. Victoria Thomas, casting director for both that film and 42, says Tarantino turned to her after Boseman’s audition and said, “That guy is going to be something.” Of all the unfamiliar actors the director saw, Thomas recalls, only Boseman earned such praise.

For 42, Brian Helgeland, the writer and director (he also wrote Mystic River and L.A. Confidential, for which he won an Oscar), wanted an unknown actor in the lead. “I just have a much easier time buying into the whole thing when the actor is not very well known,” he explains, arguing that otherwise, “the audience is trying to get past the person they know and into the movie.”

This time Boseman nailed the audition—in part, Helgeland recalls, by opening with a particularly harrowing scene: an infamous incident in which Ben Chapman, manager of the rival Philadelphia Phillies, hurled a series of brutal epithets at Robinson during a game against the Dodgers. Enraged but stone-faced in public, the ballplayer smashed a bat and erupted in tears once off the field. “It was such a brave choice,” the director says, “and I thought right away, This is the guy.”

But first, Boseman needed to complete a baseball tryout held at Jackie Robinson Stadium on the campus of UCLA, Robinson’s alma mater. “They were actually like, ‘See the statue up there? Do you realize how big this is?’ ” Boseman says, laughing. “It was really scary.” Adds Helgeland: “That was probably in hindsight too much pressure to put on him.”

But then, Robinson too operated under excruciating pressure. When he signed with the Dodgers, he pledged never to take the bait when confronted with the rampant racism he would face. For this reason, “he can’t say a lot,” Boseman notes, “so a lot of it is internal. That was the difficult thing about the role.” To keep the scene with Chapman as authentic as possible, Boseman refused to talk to actor Alan Tudyk, who played the race-baiting manager, during shooting.

Chapman’s rant is difficult to sit through. He unleashes every racial slur and plays off every stereotype in an attempt to rattle Robinson. Nonetheless, when Boseman heard Tudyk rehearsing the lines, he would start laughing. “Because it was so absurd,” he says. “The word n—– doesn’t have power over me. And I’m not sure it’s what would have bothered Jackie Robinson as much as [the fact that he] was being disrespected. Because you’re talking about a man who was extremely proud.”

To Boseman, the film’s message is clear: Robinson tested America. “Without bringing black players into the majors, your scorecard is not accurate,” he says. “And it’s not just the scorecard of the game, it’s the scorecard of the whole nation. Is the nation living up to what it says it is?” Boseman hopes the film inspires more African Americans to take up baseball. Robinson sacrificed much to integrate the national pastime, but the number of black players in the major leagues has been declining for years. At the beginning of the 2012 season, just 8% of major league players were African American, according to USA Today. In 1975, the figure was 27%.

To prepare for the role, Boseman devoured books about Robinson and watched hours of footage of him on and off the field. He sat down with Robinson’s 90-year-old widow Rachel, who founded the Jackie Robinson Foundation, which provides college scholarships for disadvantaged students. One tip she gave him: Jackie would put his hands on his hips as though surveying the world on his own terms. Rachel, who has seen prior efforts to bring her husband’s story to the big screen fall through, liked Boseman immediately but was still apprehensive. “I didn’t know if a young actor who was getting into a major production for the first time could convey him,” she says.

That concern evaporated when she screened the film. “I was thrilled by Chad’s depiction of Jack,” she says. “I was moved to tears by the performance. I felt the warmth and passion that Jack and I felt for each other. It’s quietly portrayed. I cherished it so much.”

And, she adds, “it inspired me to think that this is the beginning of a larger professional role for him in the movies.”